William Llewellyn was the son of a Llantrisant family of butchers and chemists but followed a career as an accountant. He married Mary Morgan of Swan Stores in Llantrisant and their mutual understanding of businesses and retail saw them create the famous Gwalia stores at Ogmore Vale.

In 1880 William Llewellyn developed his grocery business by building the shop. The original building was flanked by the storeroom and Llewellyn's house.

The shop was fitted with mahogany shelving, counters and bins by Parnalls of Bristol, and by 1912 the ground floor of the house had been taken over and a drapery established.

The shop soon expanded to include the first floor and the ground floor of the adjoining three houses.

By 1916, Gwalia Stores comprised a bakery, ironmongery, grocery, gentlemen's outfitters, chemist and a section selling animal feeds. Members of staff slept in the attics and were paid 8 shillings (40p) per week.

Such was their success that Llewellyn bought a Rolls Royce which had belonged to King Edward VII. The couple had eight children.

Alderman Llewellyn died in 1924. His Gwalia Stores closed in 1973 and was moved to St Fagan’s museum in 1988.